Independent / third-party ROMs for android phones do exist, but they tend to be hobbyist in nature. If you're the guy who runs linux on all your machines, great! If you just want basic shit, not so great.
The real issue isn't features, it's security. You can live without features. But every time a really bad bug gets discovered for android, a bunch of people who paid $700 just a year or a year and a half ago get told "sorry, we don't care about you."
Every high-end phone these days can live a long time - aluminum is strong - but iphones and amazon devices are the only ones that get updated for more than three years are so. (Yep, amazon really cares about security, believe it or not.) Even nexus/pixel devices will only get maybe two years of support. Anything from samsung might get a year and a half. Anything from anyone else ... you'll be lucky to get three software updates before they drop you. And then the next big security bug that gets discovered affects you, forever, until you trade the phone in.
Iphones have a high resale value for a reason.
In any event, fortunately/unfortunately (pick one), in today's connected world, a young teen or just-before-teen (tween?) isn't getting a phone to keep up with the joneses, it's to constantly talk to classmates and friends. If you remember running around outside all day with your friends, today you'd be IMing them all day. To look down on it as not needed, because "you don't need to call us [parents] because you're only going to school and sports practice," is doing them a disservice. If you don't want them to constantly talk with their friends, that's all well and good, but you should know precisely what you're forbidding, and not misunderstand the situation.